Manufacture of pneumatic tire casings



G." L; MATHER 1;921,474

MANUFACTURE OF PNEUMATIC TIRE CASINGS Aug. 8, 1933.

Original Filed Feb. 1928 2 Sheets-Sheet 1 INVENTOR. GEORGE L. MATHE'R.

BY WW A TTORNE Y.

Aug. 8, 1933.

G. L. MATH ER MANUFACTURE OF PNEUMATIC TIRE CASINGS Original Filed Feb.2, 1928 2 Sheets-Sheet 2 INVENTOR.

,G'EOPGE L. .ZIMTHE'P.

ATTORNEY.

Patented Aug. 8, 1933 Iii ; err-Es TENT oFFicE MANUFACTURE GI PNEUMATICTIRE CASENGS George L. Mather, Milwaukee, Wis, assignor to The FishRubber Company, hicopee Falls,

Mass, a Corporation of Massachusetts Original application February 2,1928, Serial 251,343. Divided and this application March 11, 1929,Serial No. 346,004. Renewed December 6, 1932 Claims.

carcass, I locate the bead edges substantially the same as if the restof the carcass structure were to be assembled in flat annular formaccording to known practice, except that my head edges are closertogether. That is to say, the bead portion assembly is not a feature ofmy invention, but the assembly and shaping of the flexible portions ofthe carcass material between the bead portions are features of myinvention. I shape the carcass material adjacent the bead edges asarched portions and as if the whole cross-section were to be of archform from edge to edge. These arched portions extend from each beadportion toward the other a suificient distance to locate the greaterpart of the carcass material in a substantially larger annulus than thatin which the beads lie, and the greater part of the carcass material,thus located, is shaped in flat form out or" the central portion of mycarcass material as it is assembled. This particular procedure and itspurpose will be clearer from an explanation of the accompanyingdrawingsin which,

Fig. 1 shows a cross-section of a tire building drum on which myinvention may be practiced, a finished tire carcass section being shownon the drum;

Fig. 2 is a diagrammatic view showing certain features of the prior artpractice with respect to 5 fiat drum building;

Fig. 3 is a view similar to Fig. 2, but showing in contrast thereto thedesired practice made available by my invention;

l is a diagrammatic View of a strip of cord fabric illustrating what istermed the angle of out; and

Fig. 5 is a diagrammatic view of the crown portion of a tire carcassillustrating what is termed the finished angle of. the cords.

My tire former is generally indicated at 10 and comprises a fiat raisedcrown portion 11, bead receiving portions 12 and arched portions '13connecting the portions 11 and 12. The former is preferably madeadjustable as to width as at 14. The bead edges or portions of the tirecarcass are shown at 1 and they are characterized as usual by being therelatively inflexible and immovable anchor portions of the carcass. Thearch-shaped portions adjacent the beads are shown at 2 and arecharacterized by their relative flexibility as forming a part at leastof the sidewall portions of the carcass. The central portion is shown at3 and this is characterized by its flexibility as forming the tread andany part of the sidewall structure not included in portions 2. My methodis characterized by the relative manner in which the portions 2 and 3are formed.

The purpose of building the carcass in this particular form will bedescribed in detail. Such detail will bring out additional and preferredfeatures of the invention both in regard to the method and the buildingformer. v

the building of cord tires of large crosssection, it has been found thatflat building methods for assembling of the carcass make difficultiesbecause when the tire carcass is built with a flat cross-sectionthroughout its flexible portions and then shaped according to knownmethods, the extreme movement which the carcass portions need toundergo, in order to pass from their annular but flat cross-sectionalform to their doubly curved tire form, causes an objectionable degree ofrearrangement of the individual cords so that the ultimate tire is quitefrequently not what is desired in balanced tire formation. This fault isincreased when the tire parts are originally assembled by the fiatbuilding method and the tire shaped by expansion is not only of largecross-section but of relatively small rim or bead diameter. This latterrequirement in many" balloon tires causes an extreme curvature of thetire walls in their final form, which increases the necessary movementsof the carcass material when shaped from the fiat annulus up to tireform. As a result it has been the usual practice to build only therelatively small sizes of tires by the flat building method, using forthe larger tires the old core method involving a core on which thecarcass materials are assembled and at the same time shaped by spinningopera tions to approximately the form of the finished tire.

According to my method I assemble the carcass materials preferably on mypeculiarly shaped former so that the arch portions 2 incline upwardlyfrom the bead portions far enough to space the fiat or central portionof the carcass 3 outwardly from the bead diameter enough so that thisfiat portion can be readily shaped as a unit by any of the known meansused in the flat building methods and without trouble due to excessivemovements of the parts. It should be appreciated that this trouble isavoidedby the fact that in building the larger sized tires, to which myinvention particularly directed, each ply, or pair of plies, may be onlyslightly expanded as it is placed on the drum, and the method ofexpanding the whole carcass as a unit is used only for that range whichexperience has proved to be practicable and suitable for the adjustmentof the moled carcass material. In this respect the entral portion of myrelatively large carcass is shaped with all the advantages that smallerti-e are with. This central portion has s integral with the arch-shapedportions, which act somewhat as if they were the bead edges of my tirein the shaping operation because they do not need to move enough tocause any dirli ulties, having already been shaped in the assemblingoperation in anticipation of the require; ent that the expansion shapingsteshall be confined primarily to a limited portion of the flexibleparts of the large carcass.

Due to the fact that the arch-shaped portions when assembled are given adouble curvature approximating the double curvature of the tire formd-on, it not necessary in the final for them to move much more thanwould ve been the case had the whole carcass been assembled and shapedon a core. Due to the fact that the side portions do not need to bemoved much with relation to the central portion, they V serve as abuffer between the flat central porby my method build a tire I sizedtire Y better quality than the same size built on any of tion w is giventhe extrem shaping operation and the bead edges which anchor the carcassfor the shaping operation.

I have found by actual experiment that I can with much greater facilityon my former than the same tire of pproximately equal quality can bebuilt on a tire shaped core; and I have found that the large iltaccording to my invention has the so-called fiat building formers nowgenerally in use, other things being approximately equal.

Following this experimentation, tires have actually been built accordingto my method in large quantity on my particular building former, withoutencounte e the di'. .culties above mentioned, and put 0 use withentirely satisfactory results. I believe this to be due in part at leastto the following procedure which is con- 3 sidered of advantage in thepractice of my method: in laying up the carcass laminations I build twoor more of cord fabric with the angle of the cords in one ply reversedwith respect to the an le of the cords in an adjacent ply, eachlamination being in the form of a flat pr determined length or in theform of ular band formed by joining the ends A sac-prepared laminationwhether in the strip or annular form is termed a pocket and the pocketdiameter is the diameter of the pocket when in unstretched annular form.The diameter of this pocket is slightly less than the diameter of theflat portion ll of my building former. I stretch'the pocket either instrip or annular form onto the building former so that its centralportion contracts tightly against the flat portion of the former and dueto the smaller diameter of the pocket its edges or skirts fall downslightly toward the arch surface portions 13 of the former. The lattercan be truly shaped to the former by simple rolling or stitchingoperations as a plurality of these pockets are assembled on the former,the beads can be tied in at the edges and the carcass shaped in unitform as shown in Fig. 1. The carcass material may,

if desired, be wound on the building former a ingle ply at a time, thepocket diameter being the diameter of the circlev of which theunstretched ply length is the circumference.

While I prefer the arch-shaped portions 2 curved transversely of theformer, as shown, it is apparent that the curvature thereof may beincreased, or flattened out, without departing from the scope of myinvention so long as the partially shaped skirts formed between the iiatcentral portion and the bead edges of the the are of an extentsuiiicient to enable me to start the unit shaping operation of the flatcentral portion far enough beyond the beads to avoid causing such aninternal movement of the cords in taking ultimate tire shape that theresulting diniculties will outweigh the advantages to be gained bybuilding methods for tires for large crossscction.

In carrying out my method I prefer the as sembly at the bead edges to bemade in the relative position shown in the drawing". This beadarrangement, briefly stated, is for the purpose of preventing anexcessive rolling action of the beads or a pivoting of the carcass aboutthe bead wires during the expansion of the tire to shape, and aims topartially substitute therefor a hinging action approximately at thepoints The exact building position desirable for the heads up to thepoints 4 diifers for different types of bead construction and inapplying my invention it is not necessary to depart from the bestpractice in this regard as shown by the prior art. Bead arrangements tosecure a simple hinging action have been used with the flat building 7drums of the prior art and it will be understood that my invention dealswith the flexible portions of the carcass lying above the hinge.

The broad scope of my invention and the substantial advantagescommensurate with the breadth of the invention have been clearly shownabove. My broad method and novel former further make available certainparticulars of improved tire construction which will now be de scribed,heretofore obtaintable in tires of large cross-section only by buildingthem by the core method.

As previously stated, a tire casing is formed of a plurality of plies ofcord fabric, the cords of each ply crossing the crown of the tire at anangle to the center line of the tread, the cords of alternate pliesbeing inclined in opposite directionsi The plies of cord fabric are cutto the desired width from a web of cord fabric, the

strips being cut on the bias and the angle of the cut preferably beingrelated to the angular relation of the cords at the crown of thefinished, tire in a manner which will be briefly discussed.

In order to secure the desired functioning of the cords in the finishedtire it is necessary that The degree of stretch impart-er. be consideredas the increase area of the fabric ply in the finished tire over itsarea in an unstretched condition. One element or factor of this stretchis the longitudinal stretch imparted to fabric at the crown of thecarcass of the finished tire; for our present purposes thiscircumferential stretch is taken as the criterion and is measured as theper cent of increase in the finished crown circumference over thecircumference of the unstretched pocket, or length of strip, of the urn,

stretched fabric forming the carcass ply. I For given materials and tireconstruction it is an advantage to have the per cent of circumferentialstretch constant for substantially all sizes of tires. I That is to say,in building large size tires this stretch should be no more or less thanin building small size tires if the material is the same. This per centof stretch I will call I).

Referring to 5 of the drawings which diagrammatically shows the positionof the cords at the crown of a finished tire I have esignated as a theangle at which each cord crosses the center line of the tire. Tests havedemon trated that for a given type of tire this angle a should be thesame in large size tires as in small size tires. Turning now to Fig. 4which shows diagrammatically the position of the cords in theunstretched strip of cord fabric it comes from the bias cutter, I havedesignated as c the cord angle coir"- sponding to a in the finishedtire. Bearing in mind that the tire carcass is made up of a plu ralityof plies, the cords of which are inclined in opposite directions, itwill be seen that the circumferential stretch applied to the tirecarcass tends to swing the cords toward the center line of the tire, inother words to get a finish angle a at the crown of the tire afterimparting b pe cent of stretch we must start with a cord angle 0. It isa decided advantage from a manufacturing point of view, regardless ofthe advantage in the finished tire, that c be constant for all sizes oftires since the fabric may then be cut for all sizes of tires with onesetting of the bias cutter. This results in substantial savings inhandling material under mass production methods.

In Fig. 2 I have diagrammatically illustrated the prior art drum in itsrelation to t -e three factors, a, b, and c, just discussed, the drum bing indicated in sectional profile at 6. The drum has a substantiallyuniform diameter 1 which is substantially equal to the bead diameter dof the tire to be built, shoulders being provided to position the beads7 of the tire carcass 8 in the manner above refer ed to. At the presenttime there are seven or more sizes of tires having the same rimdiameter, that is, seven on an 18 inch rim, seven on a 19 inch rim,eight on a 20 inch rim, etc. In Fig. 2 I have shown in dotted line twosizes of tires of bead diameter d and outside diameter e and 6 Thediameter of the pocket or ply of unstretched carcass fabric isdesignated h and obviously cannot be greater than the diameter of thedrum. It is clear from an inspection of the figure that thecircumferential stretch imparted to the fabric in bringing the crown ofthe tire to the diameter e will be less than in bringing it to diameterc and that if the cord angle 0 of the pocket having it diameter is keptconstant in building both tires the finish angle a at the crown of thesmall tire must differ from the finish angle a of the large tire andconversely, if the finish angle a is kept constant the cord angles 0must differ.

This illustrates the limitation of the old drum. For a single size tireon the diameter d, for instance 2 the stretch from pocket diameter h tofinished tire diameter e may equal the percentage of stretch b which iscalled for by desired practice and the desired angle a can be had byproperly choosing c. It may be that tires difiering only slightly insize from c may also be built on the drum 6, but it clear that the valueof b will increase asthe size or" the tire increases (and 'in largesizetires this increase of b attains sub stantial proportions), sincethe circumferential stretch that is imparted to the carcass when it isexpanded is increased by the increased circumference at e over that at eReferring to Fig. 3, I have diagrammatically illustrated how my improveddrum permits the building of any size of tire and also permits a controlof the values of a, b, and c to the end that all three may be keptconstant regardless of the size of tire built. At 9 I have indicated mydrum in profile section with a tire carcass positioned the con and indotted line I have indicated two sizes of large tires 6 and c Due to theincreased diameter 1 of my drum over that of the drum of Fig. 2, it ispossible to increase the pocket diameter h to a diameter b or k suchthat the stretch b is the same in bringing 7Z2 to diameter 2 or inbringing 71 to diameter 6 It will also be evident that with a constantboth a and 0 can be lrept constant. The required value of h for a givensize of finished outside tire-diameter e be derived as follows:

"-lere b is the constant per cent of stretch deired. It will be notedthat when the stretch is :ept constant for all the sizes that the valueof he cord angles at the crown or" the finished tire Obviously when k isequal to 0, f is equal to h. The number of sizes of tires which be builtona given former depends on the value of is permitted by the buildingconditions imposed by the tire building instrumentalities used, the tirespecifications and the extent to which the former may be adjusted forwidth. The value of k for a given support and given tire size may bederived from (2) and (3):

f-h f(1+b)-e From the above formula it is evident that according to myinvention a drum may be made for each different size, keeping a, b, c,and 7c constant, or that within the limits of the mechanical adjustmentof the width of the drum and the variation in is permitted by goodpractice, one drum may be used for several sizes of tires. For example,it has been found that for 28 X 4.75, 28 X 4.95, and 29 X 5.00 on a 19inch rim a single former of 21.647 inch diameter may be used withconstant values for a, b, and c, and k varying between 2.8% and 2.0%.Larger sized tires both on smaller and larger rim diameters have beensuccessfully built according to my invention, examples being 36 x 6.20for an 18 inch rim, the crown diameter of the building former being22.551 inches, and a 32 X 6.75 for a 20 i' ch rim, the crown diameter ofthe building fcriirr being 24.532 inches, the values of a, l), 0 beingthe same in all cases.

It will thus be seen that in addition to making it possible to securethe substantial advantages of flat building methods in the building oflarge tires, my invention makes possible a nice control of the buildingfactors.

Having thus described my invention, I claim:

1. A method in the building of cord tires which consists in assemblingrubberized cord layers and bead members into annular form and during theassembly shaping said layers into partial tire form comprising a carcasshaving a hat central portion of substantially larger diameter than thebead diameter and inwardly and upwardly inclined arch-shaped portionsbetween the bead edges and the flat portion, said arch-shaped portionscomprising a major portion of the tire sidewalls, the rise from beaddiameter to larger diameter being through said arch-shaped portionswithout sharp curvature and in finishing said carcass formation byforcing the flat crown portion and partially shaped sidewall portions totire form as a unit and simultaneously swinging the inclined sidewallportions into finished position by a hinging action approximately alongthe lines where said sidewall portions join the central flat portion.

2. A method in the building of cord tires which bead members intoannular form and during the assembly shaping layers into partial tireform in an upwardly and inwardly inclined. position from t e hinge ofthe beads to points a central portion, the upwardly and inwardly Uioncompr major portion of .all and i g carcass formation by for: "g thefiat central portion and the partially forme sidewall portions to tireform as a unit ieously swinging the inclined sidewall portions intofinished position by a hinging action appr-i ately along the lines wheresai sidewall portions join the central fiat portion.

3. A method in the building of cord tires which consists in assemblingrubberized cord layers and bead members into annular form. and duringthe assembly shaping said layers intop'artial tire form in an upwardlyand inwardly inclined position from the hinge of the beads through amajor portion of the tire sidewalls and until a point is reached suchthat the remaining flat carcass portion is spaced above the bead hingessuiiiciently to permit its being expanded to tire shape as a unitwithout undue rearrangement of the cords.

a. A method in the building of cord tires which consists in assemblingrubberized cord layers, the cords of which lie at a predetermined angletransversely of the layers, and bead members into an annular form andduring the assembly shaping said layers into partial tire form in anupwardly and inwardly inclined position from the hinge of the beadsuntil a point is reached such that the degree of expansion required toform the remaining flat portion to tire shape will bring the angle ofthe cords at the crown of the completely tire to a predeterminedstandard angle irrespective of the size of the tire.

5. The method of building cor-:1 tires of various sizes but having thesame cord angle at the crown of the finished tire and having the samepercentage of surface stretch imparted to the cord plies, which.comprises cutting the cord plies at the same angle regardless of thesize of the tire to be built, said cuttin angle being that angle fixedby predetermined angular position of the cords desired at the crown ofthe finished tire and by said predetermined percentage of stretchdes'red in the cord plies of the finished tire, assembling the so cutplies and bead members into annular form and du ing the assembly shapingthe into a partial tire form having a flat central. portion of adiameter larger than bead by an amount at least suiflcient to permitsubsequent unit expansion of the flat central to finished tire size andshape without imparting thereto a stretch in excess of that fixed by theangle of out and the desired finished angle, and sufficiently in excessof said amount to prevent undue rearrangement of the cords during saidunit shaping operation, the pocket diameter of the plies being less thanthe diameter of said fiat central portion by an amount sufficient toimpart a percentage of stretch to the plies during their assembly tocompensate for any excess diameter of said fiat portion and make thetotal stretch to the piles during their assembly and 1 subsequent unitshaping to complete tire form equal to that desired in the finishedtire.

GEGRGE L. MATHER.

